This invention relates to a hydrogenation catalyst containing cobalt, manganese, copper, alkali and silicon dioxide a process for its preparation and its use for the preparation of dicyclohexylamine.
German Pat. No. 1,568,188 discloses a catalyst which contains cobalt and manganese in the form of oxides on pumice and which is used for the catalytic hydrogenation of 4,4'-diamino-3,3'-dimethyldiphenylethane. Furthermore, German Published Specification No. 2,314,813 discloses a catalyst which contains cobalt, manganese and, optionally, copper and which is used in the preparation of d,l-menthol by catalytic hydrogenation of corresponding unsaturated compounds.
Dicyclohexylamine can be obtained in accordance with the process of German Pat. No. 805,518 by catalytic hydrogenation of aniline in the presence of a nickel catalyst; the by-products obtained at the same time are cyclohexylamine and cyclohexanol. The catalytic hydrogenation of diphenylamine to cyclohexylamine using a nickel catalyst is also known (J. Amer. Chem. Soc. volume 53, page 1869 (1931); Chemical Abstracts, volume 67, 43121r (1967)); however, here again considerable amounts of by-products are obtained. None of the known processes gives a dicyclohexylamine which can be used without additional purification.
There is, therefore, a great need for a better catalyst which makes it possible to obtain directly a pure dicyclohexylamine by catalytic hydrogenation of diphenylamine.